Method for estimating damage to an object, and method and system for controlling the use of the object

ABSTRACT

A communication system between a base station and a plurality of pieces of construction equipment, the communication system including a transmitter and receiver for transmitting measured operational information from the plurality of pieces of construction equipment to the base station. Each equipment piece includes an operational component that is susceptible to damage. A computer based controller is utilized for measuring a plurality of operational parameters of a respective equipment piece and communicating derived measured operational information. A calculator is used for calculating an amount of damage incurred by the component based on the communicated measured operational information concerning the respective equipment piece.

CROSS-REFERENCE TO RELATED APPLICATIONS

“The present application is a continuation of patent application of U.S.application Ser. No. 10/710,592 filed Jul. 22, 2004, now U.S. Pat. No.7,194,384, which is a continuation of patent application of U.S.application Ser. No. 10/248,459 filed Jan. 21, 2003, now abandoned,which is a continuation patent application of International ApplicationNo. PCT/SE01/01624 filed Jul. 16, 2001 which was published in Englishpursuant to Article 21(2) of the Patent Cooperation Treaty, and whichclaims priority to Swedish Application No. 0002723-5, filed Jul. 20,2000. All of said applications are hereby expressly incorporated hereinby reference in their respective entireties.”

TECHNICAL FIELD

The present invention relates to a method for estimating life reducingdamage to an object which is subjected to a load during operation. Themethod considers at least a first parameter that corresponds to anoperational state that generates such damage to the object and at leasta second parameter that corresponds to a condition for, or around anobject that, by itself, is not able to generate the damage but whichmakes the damage generated by the operational state worse. Thedetermination is made by at least one operation that is measurement, andsuch measurement is carried out repeatedly. The invention also relatesto a system and method for controlling the use of the object.

The invention can, for example, be applied in a means for transport,such as a vehicle, a vessel or another means of transport, such as meansfor transport on rails. The word vehicle relates to various groundvehicles, such as vehicles with wheels or tracks. The invention is, inparticular, suitable to be applied to a construction machine such as awheel loader, an excavator or an articulated hauler also known as adumper—each of which is commonly referred to individually as anequipment piece, or alternatively a piece of construction equipment. Thearea of application of the invention is, however, not limited to theseapplications; it can also be applied in stationary devices.

Below, the invention is exemplified utilizing a rotating means in thegear box of a vehicle as the object of interest. The invention in thiscase relates to the calculation of surface fatigue of the teeth and thebearings, respectively. This should be seen as a preferred, but in noway a limiting application of the invention.

Exemplarily, the first parameter that corresponds to an operationalstate for the object relates to a parameter that on its own can generatedamage to the object. By the word “damage”, weakening of the object isintended, or in other words a reduction of the useable life of theobject. An example of such an operational state is a torque transferredto the object during a number of revolutions. Other examples of such anoperational state are various types of forces which come to bear on theobject.

The second parameter that corresponds to a condition occurring at theoperational state relates to a parameter that on its own would not causeany damage to the object. It is only in combination with the firstparameter that corresponds to an operational state for the object thatit can make the damage to the object worse. Examples of such conditionsare the environment around the object, for example the amount ofparticles, such as metal filaments produced and present in lubricatingoil.

BACKGROUND

The effect on the life of a gear wheel by an applied torque during anumber of revolutions can be calculated by conventional means. It isalso appreciated that specific parameters corresponding to operationalconditions for the gear wheel with applied torque will affect itssusceptibility to damage. That is, this condition has an effect on thedamage caused by the applied torque during revolutional operation of thegear wheel. An example of such an operational condition is thetemperature of oil used to cool the gear wheel during operation. Knownmodels for such calculations, however, lack precision.

DISCLOSURE OF INVENTION

A primary purpose of the invention is to provide a method for predictingthe influence of a plurality of parameters on the life of an object thatgives higher precision than known methods when calculating the remaininglife of the object after a certain amount of use has occurred. Asecondary purpose of the invention is to obtain a method that generatesvalues on load and/or damage that in a storage-efficient manner can bestored in a memory with limited memory capacity.

These purposes are obtained by a total load which is defined by thetotal effect on the life of the object by the operational state and theoperational condition is calculated in such a way that variations in thedamage resistance of the object which the operational condition givesrise to are adjusted for, and the total load is expressed as a productof a function for the operational state and a function for theoperational condition. The total load is thus a measure of a simulativeinfluence of both the operational state and the current operationalcondition(s), which creates the conditions for high precision, sincethere in reality is an interaction between the operational state and theoperational condition.

These other parameters, for example temperature, particle load and watercontent of the cooling medium can have large influences on the damagethat a specific load causes to the object. A calculation of theremaining life based on both (1) the load that is defined by the firstparameter and (2) the condition that is defined by the second parameterpermits high precision predictive calculations. In more detail, theinvention takes into consideration the variations in the susceptibilityto damage of the object which is caused by the other parameters.

In so doing, conditions are also created for storing a result of thecalculation based on the first parameter that corresponds to a load, anda plurality of other parameters which affect the susceptibility todamage of the object in a position (cell) in a memory unit. This leadsto a reduced need for memory.

According to a preferred embodiment of the invention, the total load iscalculated multiple (a plurality of) times during the period over whichthe measurements are taken. This results in a further reduction inmemory requirement since a reduced number of measured values need bestored. This also causes a higher precision in estimating the damage.Preferably, the calculation of total load is carried out continuouslyduring the time that the measurements are taken.

According to another preferred embodiment of the invention, the totalload is calculated after each determination of the first parameter. Sucha determination can in practice be a measurement of the first parameter.Only one value, the calculated value for the total load, is then savedfor each increment in time. This creates the conditions for an even moreefficient memory unit concerning memory space.

According to another preferred embodiment of the invention, thecalculated values are summed for the total load, and the result isstored in a first field in a memory unit. This creates the conditionsfor a continuous or on-line control of the influence of both theoperational states and the operational conditions. This feature is notlimited to storing only the result, but at least the result of thesummation is stored.

According to a further development of the previous embodiment of theinvention, the second parameter is assumed to be constant during aplurality of measurements of the first parameter in a furthercalculation of the total load, and the total load is calculated with thesecond parameter at the constant value, the calculated values aresummed, and the result is stored in a second field in the memory unit.In this embodiment, the second parameter is suitably set to a value thathas been measured in real tests. For example, this embodiment can beused as the basis for future dimensioning of the object/a devicecomprising (including, but not necessarily limited to) the object. Theembodiment is used in cases with small variations in the operationalconditions.

According to another preferred embodiment of the invention, the numberof load cycles are measured for the first parameter, and in a matrix ina memory unit which matrix comprises a plurality of different positionswhich each corresponds to a specific operational state and at least onespecific condition, the number of load cycles are added in therespective positions. Suitably, a matrix is used which has a number ofpredefined levels of the operational state on a first axis and a numberof predetermined levels for the operational conditions on a second axis.The matrix can be expanded for further operational states to ann-dimensional matrix. If a first parameter and two second parameters aremeasured, a three-dimensional matrix is used.

By means of this embodiment, the measured values can be stored in amemory unit, for example in a vehicle which comprises the object (anoperational component) and can then at a later point in time betransmitted or transferred to a unit for calculating the total load.This embodiment permits a fewer calculations to be necessitated at thevehicle.

According to another preferred embodiment of the invention, at least oneof the first and the second parameters are described as an exponentialfunction. This creates conditions for a simple, and regarding memorycapacity, efficient way to express the total load with high precision.In addition, conditions are created for using the Palmgren-Miner partialdamage theory.

According to another preferred embodiment of the invention, a total lifeinfluencing damage in the object is calculated after a certain amount oftime as the sum of each of the calculated total loads before this pointin time. This life influencing damage can be used in a number of variousways. For example, information regarding the remaining damage can bepresented directly to the driver of the vehicle so that he is aware ofthe status of the object. This can lead to a milder operation of thevehicle/object. He can furthermore decide on continued operation of thevehicle, exchanging or repairing the object and the like. Theinformation is suitably presented on a display to the driver. Accordingto one alternative, an electrical device such as a computer is connectedto the vehicle for presentation to service personnel, the system'sowner(s) or other interested parties.

According to another example, this information is transmitted to a basestation or a central terminal. This makes it possible to control thestatus of a plurality of vehicles and to plan their continued operation.When renting the vehicle, charges can be calculated based on damage orreduced life caused by the renter's use.

According to another preferred embodiment of the invention, the firstparameter is measured at a higher frequency than the second parameter.In other words, the first parameter is measured at shorter intervals intime than the second parameter. A measured value for the secondparameter is in this case used for calculating the total load forseveral measured values of the first parameters that follow each otherin time. In this way, the number of necessary measurements is reduced.This is particularly preferred in cases when the second parameter, atleast in periods, varies within a relatively small interval.

A further purpose of the invention is to obtain a system forcommunication between a base station and at least one remotely locatedstationary or mobily arranged machine, via transmitting and receivingmeans for controlling the operational status of the machine.Exemplarily, the machine comprises an object which is susceptible todamage, and the system creates conditions (institutes certain actions orcontrols) for controlling the operational status of the object at aposition remote from the object. In particular, a system for predictingmalfunctions or breakdowns of the object and taking measures before suchmalfunctions occur is afforded by implementation of the invention.

Exemplarily, this purpose is obtained by a system comprising a controlunit, means for measuring a plurality of operational parameters of theobject, and means for calculating damage done to the object based on themeasured operational parameters.

Further preferred embodiments and advantages of the invention willbecome evident from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail below, with referenceto the embodiment(s) shown in the appended drawings, in which:

FIGS. 1-4 show four graphs, each of which illustrate load strengthfunctions as indicated thereon;

FIG. 5 is a diagrammatic view a system configured according to thepresent invention; and

FIG. 6 is a block diagram illustrating an exemplary unit of the systemthat may reside on a carrying vehicle.

MODE FOR THE INVENTION

The word “damage” refers in the following to a weakening of an object,or in other words, a reduction in remaining useful life alsocharacterized as wear-damage. The term “operational state” refers to aload which, by itself, can inflict damage or reduce the remaining lifeto the object. In other words, a strength (also known as damageresistance) of the object is reduced when it is exposed to a load. Thestrength is at each point in time dependent both on the internalstructure or make-up of the object, such as, for example, its materialof construction and/or the operational conditions or environment inwhich the object performs or operates. Thus, operational conditions, ontheir own, do not cause damage (at least of the type which is presentlyof interest or being measured) to the object, but can enhance orotherwise foster damage caused by a corresponding operational state.

The object is exemplified in a first embodiment of the method by acomponent in the powertrain of the vehicle. In particular, surfacefatigue of the teeth on a gear wheel in a gear box is intended. Theoperational state (in the following called the first parameter) is thetorque that the gear wheel transfers during a number of revolutions.

The strength of the object depends on the supporting ability of theflanks of the gear teeth. The strength can be influenced by severaloperational conditions (in the following called the second parameter),and include such things as: (1) temperature, which can reduce theviscosity of the oil and thus the supporting ability of the oil film;(2) particulate load (especially those particles larger than thelubricating thickness); and (3) water content in the oil.

Below, a method used for making calculations in a first embodiment ofthe invention, and the theory therebehind, is described with referenceto the appended drawings. In this embodiment the first and the secondparameters are measured repeatedly.

The object that is exposed to the loads has, according to thedescription above, a so-called varying (variable) strength. First amethod is described that deals with so-called constant strength. Theterm “constant strength” of the object means that the damagesusceptibility of the object is not influenced by the environment or theconditions that it is in. Therefore, an explanation is provided of avarying strength of an object occurring with respect to a preferredembodiment of the invention's application.

In the instance of constant strength, many life functions can bedescribed as exponential functions. The Wohler curve, also called the SNcurve, is a well known example of fatigue in the case of a load havingconstant amplitude (See FIG. 1 in which logarithmic scales areexemplified). An exemplary relationship is defined by:S ^(m) *N=C   (1)where

-   -   S=signal level, for example tension, torque    -   N=the number of cycles to fracture    -   C=a constant for a certain curve

The constant C can be considered a measurement of the object's tolerancefor damage; that is, the amount of damage that can endured (absorb)before a fracture occurs. This is, in other words, a measurement ofstrength.

Real loads are often applied with variable amplitude and are referred toas spectrum load(s). This can be described by means of thePalmgren-Minor partial damage hypotheses (See FIG. 1):Partial damage value=Σ(ni/Ni)=p   (2)where

-   Ni=he number of cycles to fracture at the signal level Sl-   ni=the number of load cycles in the spectrum at the same level Si-   p=partial damage value=1 in the case of fracture, often the value    0,7 is used instead or another value.

The summation is done over the entire spectrum. The fatigue limit isignored since it is a phenomenon that occurs in the case of load withconstant amplitude. In the following manner, {Equation 1} is introducedinto {Equation 2}:p=Σ(Si ^(m) *ni/C)=(1/C)*Σ(Si ^(m) *ni)   (3)

-   -   since the strength C is constant in this case.

The notion load (D) is introduced as:where D=Σ(Si ^(m) *ni)   (4)

From Equations 2 and 3, it becomes evident that p=D/C. The ratio D/Cthus indicates how large a portion of the damage tolerance which hasbeen consumed by the load D.

As described above, the strength varies in many cases. The strength can,to be more exact, vary without decreasing successively. An example ofthis is surface fatigue in the case of cogs and bearings. Logging thedamage in the form of load only, for example torque and number ofrevolutions, without adjusting for the variation in strength, will forthis reason give a relatively poor precision.

It is therefore desirable to create a method that also takes intoaccount the variation in strength.

In the instance of varying strength, there is an interaction betweenload and strength. For example, a certain torque level will cause moredamage at a high temperature (which brings about lower viscosity) of thecooling oil than in the case of low temperature. It is not feasible torecord torque and temperature separately in order to then adjust for thetemperature. For this reason, this is carried out according to theinvention in each small time interval; i.e., continuously, or “on-line”.

According to {Equation 1}, the relationship between load, signal level(for example, torque, M, or number of revolutions N) and fracture can bedescribed according to {Equation 5} in which:Mi ^(m) *Ni=Ci   (5)

The decisive difference in the case of varying strength is that thetolerance for damage Ci is not constant, but depends on such things astemperature, particle load, water content and the like. For example,different temperatures will produce different values of the strength, Ci(See FIG. 2).

FIG. 3 corresponds to tests run at the same load level at differenttemperatures. It turns out that the fatigue function can be described by{Equation 6} in which:Ti ^(k) *Ni=K1   (6)

In {Equation 6}, T is the temperature, N is the amount of cycles tofracture, and k and K1 are constants.

Tests have been carried out at the same load level, which means that thestrength, C, is in proportion to the life N, and thus, according to theillustration of FIG. 4, results in:Ti ^(k) *Ci=K2   (7)Ci=K2/Ti^(k) is obtained from formula (7) and introduced into formula(3), and thus a partial damage value p is obtained:p=Σ(Si ^(m) *ni*Ti ^(k) /K2)   (8)A reference temperature To, preferably the one at which the test iscarried out is choosen The strength is then C=Co. Thus;K2=To ^(k) *Co   (9)Formula (9) is introduced into (8) which results inp=(1/Co)*Σ(Si ^(m) *ni*(Ti/To)^(k))   (10)since Co is a constant. The expressionDkorr=Σ(Si ^(m) *ni*(Ti/To)^(k))   (11)is thus a load value which is adjusted for variations in strength to areference value.Formula (10) can thus be expressed asp=Dkorr/Co

The ratio Dkorr/Co gives a good indication of the damage portion whichhas been consumed.

Increasing to more varying strength parameters is trivial. If theparticle ratio is p, the water amount v, and q and r are exponent andreference values, respectively, then reference values are obtainedaccording to:Dkorr=Σ(Si ^(m) *ni*(Ti/To)^(k)*(pi/po)^(q)*(vi/vo)^(r))   (12)

In this embodiment, the strength function has been described as anexponential function. By so doing, simple expressions are obtained forload and strength. It is, however, within the scope of the appendedclaims to describe the strength function in another way.

It has additionally been assumed that the influence of the load and thestrength parameter on the life can each be described by means of one orseveral exponential functions, which can generally be done withacceptable precision.

Preferably, the D value is summed successively. This means that theresult can be placed in only one cell, irrespective of how manyparameters are taken into consideration. The memory need will thus berelatively small in spite of the large amount of information that isgathered. According to one application of the invention, a result of thecalculation of the total load is stored in a position in a memory unitof the vehicle. The limited memory requirement is particularlyadvantageous in applications in a transport means such as a vehicle.

Another example of applications of the invention is in the case ofcardan shafts whose strength decreases as the angle in their universaljoint increases.

The invention is not limited to the above described exemplaryembodiments; a number of further variations and modifications arepossible, while remaining within the scope of the patented.

When calculating the total load, the first parameter is related to theratio between a measured second parameter and a reference value for thesecond parameter. The reference value for the second parameter is basedon actual tests of the object. In other words, a normation is made ofthe operational conditions such as the temperature against values forthese, which have been obtained in actual testing.

According to a further embodiment, a plurality of first parameters aremeasured at each measurement, and the total load is described as afunction in which the life influence of each of the first parameters issummed. It is, for example, advantageous in the case of several torquesor several forces.

Damage to the object which results in the total load is defined by thetotal load relative to the initial damage tolerance of the object. Inother words, there is a knowledge about the life of the object or itstolerance for loads at specific operational conditions. This knowledgecan, for example, be obtained through fatigue testing.

A number of ways of utilizing the result of the calculation of the totalload/influence of the life are possible. Below, a number of examples ofpreferred methods are described.

A user of the object can be billed for damage caused to the object. Thiscan for example be used in the case of renting vehicles. Another area ofapplication for the billing is at sale. At the sale, the seller can sella system that includes maintenance, exchange privileges, and the like.In other words, it is possible to bill for a degree of usage, such ascalculated damage caused to the object. The billing can of course alsotake place based on further parameters.

According to another example, the remaining life is predicted based onthe calculated damage, and based on this prediction, a decision is takenregarding the future operation of the object. The term “futureoperation” refers to, for example, measures such as maintenance,exchange, restoration and the like. Within the term “future operation,”a change of task is also contemplated. Furthermore, the term “futureoperation” includes a direct change of the operational condition bymeans of a so-called actuator, as described below.

The task for a machine that includes a number of objects that aresusceptible to damage can thus be changed after operation during acertain amount of time so that the built-in damage tolerance for all ofthese objects, to a high degree, is consumed at the end of the life ofthe machine. In addition, the task can be changed if a breakdown of theobject is predicted to arise within the near future so that the objectis exposed to smaller load. The task for a machine which comprises twoobjects which are susceptible to damage, which objects can be exposed todifferent degrees of load in different applications, can thus be changedwhen a breakdown in a first of these objects is predicted in the nearfuture, and in such a way that the first object is relieved of load andthe second object is given more load.

Examples of these two objects can be a gear wheel in the powertrain ofthe vehicle and a beam in the supporting structure (frame) of thevehicle. An example of a vehicle that can be used in applications withsuch varying loads is an articulated hauler, a so-called dumper. Thedumper can be used in a mine, in which application its powertrain isprimarily loaded during operation, and can also be used at aconstruction site with uneven ground, in which application itssupporting structure is exposed to load to a higher degree.

By means of the prediction, vehicles in a vehicle fleet can, withincreased safety, be used in an optimal way with regard to the life ofthe comprised components within various areas of use.

According to another example, the remaining life is predicted based onthe calculated damage, and the object is valued according to predictedremaining life of the object. Alternatively, the evaluation can becarried out by a machine or a vehicle which contains the object.

According to another example, a signal is transmitted comprisinginformation regarding the operational parameters, damage caused orremaining life from a transmitter which is arranged in connection to theobject to a receiver in a base station remotely located from the objectfor a decision regarding measures for the object. This brings about thepossibility to control the status of a plurality of objects or machinesthat comprise the object. It is particularly useful in the case wherethe object is arranged in a vehicle, so that the status of an entirevehicle fleet can be controlled from the base station. From the basestation, signals can be transmitted to maintenance personnel, retailers,warehouses, repair shops, production units and the like for measuresbased on calculated remaining life of the vehicle.

According to another example, the result of the calculation is used fordesign purposes. The calculated damage can be used for validation of asimulation module of the object in operation. Alternatively, the damageis used as a basis for dimensioning future objects which are intended tobe exposed to similar operation.

In addition, the invention refers to a computer program productcomprising data program segments for carrying out the steps according tothe method described above when the program is executed in a computer.The term data program segment in other words refers to software parts.According to a further development of the invention, the data programsegments are stored on a computer readable medium. The term computerreadable medium refers to for example a disk, a CD-ROM disk or a harddrive.

In addition the invention refers to a system 1 (See FIGS. 5 and 6) forcommunication between a base station 2 and at least one remotely locatedstationary or mobile machine 3, via transmitting and receiving meansexemplarily illustrated as antennae 5 for control of the operationalstatus of the machine. As illustrated, the machine 3 is arranged in avehicle 12. The machine 3 is in more detail the driving means of thevehicle 12. The transmitting and receiving means are arranged for thetransfer of information utilizing radio waves via antennae 5.

The machine 3 comprises an object (component or aspect) 6 that issusceptible to damage. The object 6 is exemplified in FIG. 6 as a cogwheel in the transmission of the vehicle. The system 1 comprises means 7for measuring a number of operational parameters of the object 6. Acontrol unit or means (CPU) 14 is operatively coupled to the measuringmeans 7, and an A/D converter 15 is operatively coupled between themeasuring means 7 and the control unit 14. The system additionallycomprises calculating means 8 operatively coupled to the control unit 14for calculating damage caused to the object 6 based on the measuredoperational parameters. Memory storage means 9 (memory) is utilized forstoring results from the damage calculation. The control unit 14 isarranged to receive a signal from the A/D converter 15, to communicatewith the calculation means 8 and memory storage means 9, and to delivera signal to the transmitting means 4 for transmission by an antenna 5(See FIG. 6) of a receiving antenna 5 of the base station 2 (See FIG.5).

The measuring means 7 comprises a plurality of sensors for measuring theabove-mentioned operational conditions and operational states.

The calculation means 8 of the system consists of a so-called predictorthat is arranged to predict malfunctions or breakdowns of the object 6.The calculation means 8 carry out damage calculations according to thecalculation process that has been described above. The evaluation ofmeasured values, including the predictions that are thus carried outdirectly in the vehicle, and results of this evaluation are transmittedto the base station 2. Alternatively, the calculation means 8 can bearranged in the base station. In this case, the measured values arestored directly in the storage or memory means 9 for later transmissionor forwarding to the base station 2 for further processing. According toa further alternative, both the calculation means 8 and the memory means9 can be arranged in the base station.

The system further comprises an actuator 11 which is operatively coupledto the control unit 14 and the object 6. The actuator 11 serves as adamage mitigation means is arranged to influence the operationalcondition and/or operational state based on values measured by themeasuring means 7. The actuator is, in this case, a cooling device forcooling the cooling oil which is supplied to the cog wheel 6.Alternatively, the actuator can consist of a filtering unit forfiltering out undesired particles in the oil. According to a furtheralternative, the actuator is a dehydrator for removing water from theoil.

The system 1 further comprises a unit 10 arranged for taking steps thatgovern the future operation of the machine/object based on thecalculation(s). This unit 10, for example, may take the form of astation for spare parts, restoration or maintenance. In this context,the term “taking steps,” for example, refers to getting ready to remedya predicted malfunction or an exchange of the object. According to onealternative, the unit for taking preventative steps exemplarily consistsof a facility for producing new objects. The unit 10 can exemplarilycomprise transmitting and receiving means in the form of an antenna 5for communication with the base station 2.

According to the preferred example, the machine is arranged in a vehicle12 but can alternatively be arranged in a vessel or in a rail-basedtransport means. It is particularly advantageous to have the ability tomonitor/control the status of the mobile means 12.

In the following, the system is exemplarily described with respect to anembodiment in which the object is arranged in a vehicle in the form of aconstruction machine such as an articulated hauler 12. This should beseen as a preferred, but in no way limiting, application of theinvention. The base station 2 can consist of a central unit in afacility configured as a construction site. Facilities management can,from the central unit via wireless communication, control theoperational status of all the construction machines 12 within theconstruction site. By carrying out the measurements and calculations atrelatively short time intervals, the operational status of the vehiclefleet of the construction site can be controlled essentiallycontinuously. After such a control, decisions can be taken regardingmaintenance, repairs and the like. According to an alternative example,the base station is arranged to control vehicles positioned over alarger geographical area, such as a country or the entire world.

The transmitting and receiving means are arranged to transferinformation relating to the status of the machine via a transmissionsignal in the form of radio waves or via satellite communication. Thus,wireless communication is preferably used, at least in part. Thetransmitting and receiving means can alternatively be arranged foroptical connections, or connection via hardware (in stationary objects)such as via land line, cable or wire.

The transmission of information takes place either periodically or upona request from the base station. A satellite positioning system,preferably a GPS system, can be used for detecting the positions of thevehicles. In FIG. 5, this configuration is illustrated as satellites 13.

In worldwide systems, the system suitably comprises a plurality of units10 for taking maintenance or other control steps located at variouspositions in the world with the purpose of supplying a number ofvehicles within a specific area with service.

According to an alternative use of the above-mentioned actuator, thecontrol unit is arranged to directly activate it when the measuredoperational condition exceeds or falls below a prescribed maximum orminimum value for the operational condition. In other words, the damagecalculation is not used in this example.

The machine can comprise a plurality of different devices arrangedstationarily, and/or mobily, and can exemplarily take the form ofcombustion engines.

A second embodiment of the method according to the invention relates tothe influence of tension loading on an object. Tension loading can bepurposefully imposed or at least be permitted to be imposed onsupporting structures such as the frame in a vehicle. The invention canof course also be used in a supporting structure of a stationary device.

It is well known that the tension amplitude Sa, also known as thetension width may be represented as ΔS (ΔS=2*Sa), which is also aparameter that prompts the crack growth of an object under load; i.e.,controls the fatigue process, and that the mean tension, Sm, affects theinfluence of the tension amplitude. A high average tension acceleratesthe fatigue process. However, a constant average tension cannot on itsown prompt crack growth. This second embodiment is thus analogous withthe first embodiment. It is well known to measure tension on an objectunder load by means of elongation measurements, for example by means ofstrain gauges. By means of a strain gauge, only one parameter (strain)is obtained. According to the embodiment of the invention describedbelow, a measurement signal from the strain gauge is divided into afirst parameter (strain amplitude) and a second parameter (averagestrain). The first parameter causes, as mentioned above, damage to theobject. The second parameter in itself does not cause any damage, butinstead affects the damage influence of the first parameter.

The expression that the first parameter and the second parameter aredetermined by at least one operation, that is a measurement, should beinterpreted to not only comprise a direct determination by means ofmeasurement, but to also comprise a measurement followed by anotheroperation or processing of the measured parameter to calculate them.

An assumption that is independent of material of construction is used todescribe the influence of the average strain at fatigue since one, ingeneral, does not have knowledge regarding the material used. Anequation proposed by Smith, Watson, Topper (SWT) satisfies thisrequirement. SWT is a special case (ΔS (R=−1), g=0.5) of the moregeneral Walker's equation in which:ΔS(R=0)=ΔSo=S _(max) ^((1-g)) *ΔS ^(g)   (13)

-   -   where g is a constant <1 and R=Smin/Smax. Smax=Sm+Sa,        Smin=Sm−Sa, ΔS=Smax−Smin=2*Sa, ΔSo for R=0, ΔS1 for R=−1. A        rearrangement of this equation gives:        ΔS1/ΔS=Sa1/Sa=(1+Sm/Sa)^((1-g))=(2/(1−R))^((1-g))   (14)    -   In an evaluation with the Rainflow method of a measured input        signal of the strain the strain width and the average strain are        obtained. A damage value at varying load (R=−1) is:        D1=Σ(ΔS1i ^(m) *ni)   (15)    -   The expression of ΔS1 from equation (14) is introduced into        equation (15) which gives:        D1=Σ((ΔSi ^(m) *ni)*(1+Smi/Sai)^(m*(1-g)))   (16)

The Rainflow method is thus combined with a special case (the SWTequation) of Walker's equation in order to arrive at an expression forthe total load. The invention, however, is not limited to Walker'sequation, but a suitable function which adjusts for the influence of theaverage tension on the effect of the tension amplitude can be used.

The calculation is carried out successively, and the adjusted damagevalue (the total load) is successively added to the same cell in amemory unit. Thus, a method is obtained to adjust “on-line” for theinfluence of the average strain. It is in an analogous manner possibleto instead adjust to another R value (for example R=0 instead of ashere, R=−1).

The phenomena of the influence of the average strain, or alternatively,of the R value, can also be formulated in terms of fracture mechanics.The process is thus not limited to Walker's function; and therebyconstitutes a third embodiment of the invention. The maximum level atwhich a crack does not grow is defined as a threshold value. Thethreshold value is very much dependent on the R value for mostmaterials. This may be represented by:ΔK _(th) =ΔK _(tho)*(1−R)^g   (Klesnil and Lukas)or ΔK _(th) =a+b*(1−R)

-   -   ΔK_(th) is the threshold value of the strain intensity index o        for R=0. a and b are constants.    -   Another phenomena “Crack Closure” can be described as        ΔKeff/ΔK=U=c+d*R   (Elber)

In both cases, an adjustment of the life is obtained depending on the Rvalue, which can easily be described as amplitude and average strain.

Furthermore, the evaluation of the signal is not limited to Rainflow. Acombination of “Range Pair” and “Level Crossing,” or the latter alone,can yield approximating information about the R value.

According to a further development of the second embodiment, thenon-adjusted damage is added in another cell. The ratio between theadjusted and non-adjusted damage will give the influence of the averagestrain on the damage in the time plane.

It is possible to carry out the corresponding evaluation of a storedRainflow matrix. This, however, needs more memory space. In addition,this does not give as good of precision since the amount of intervals islimited.

It is important that the parameter g can be chosen. In weldingconstruction, it is assumed that residual strains are so great that theaverage strain can be neglected. In the case of spectrum load, which isin general the case, the high loads will, however, successively triggerthe residual strains, which will lead to the average strain affectingthe fatigue damage. By arriving at suitable values of the constant g, itis possible to describe this phenomena in an adequate manner.

In the following, two illustrative examples are provided of applicationsof the second embodiment of the present invention. In the first example,a flying airplane is utilized, and in which the tension load on a wingwill vary. That is, the tension amplitude around an average tensionpresent on the lower side of the wing is positive tensile stress. Thesevarying average strains will increase and decrease, respectively, thedamage effect of the strain amplitude. Contrarily, the average strainseparately will give rise to none, or very small damage influence.

In a second illustration, a load vehicle is utilized, and in which theaverage strain in supporting parts, for example frame members, dependson whether the vehicle is loaded. This influences the damage effect ofthe variation in strain that is described with its amplitude or width. Aconstant average strain does not give rise to any damage influence inthe case of fatigue. However, the shifts between, for example, twoaverage strain levels will in time contribute to damage. But the shiftswill, in the evaluation, be treated as amplitudes.

It should be appreciated, however, that the second embodiment of thepresently disclosed inventive method is not limited to estimating damageor wear to an object caused by strain load. The measurement signal whichis evaluated can be any signal, force, torque, pressure and/or the likewhich can be related to strain.

1. A communication system between a base station and a plurality ofpieces of construction equipment, said communication system comprising:transmitting means and receiving means for transmitting measuredoperational information from the plurality of pieces of constructionequipment to the base station and wherein each equipment piece comprisesan operational component that is susceptible to damage; a control meansfor measuring a plurality of operational parameters of a respectiveequipment piece and communicating measured operational informationderived therefrom over said transmitting means and receiving means tothe base station; calculating means for calculating an amount of damageincurred by the component based on said communicated measuredoperational information concerning the respective equipment piece; and adamage mitigation means for automatically adapting future operation ofthe respective equipment piece based on the calculated amount ofincurred damage.
 2. The communication system as recited in claim 1,wherein said damage mitigation means is an actuator arranged forinfluencing operating conditions of the operational component.
 3. Acommunication system between a base station and a plurality of pieces ofconstruction equipment, said communication system comprising:transmitting means and receiving means for transmitting measuredoperational information from the plurality of pieces of constructionequipment to the base station and wherein each equipment piece comprisesan operational component that is susceptible to damage; a control meansfor measuring a plurality of operational parameters of a respectiveequipment piece and communicating measured operational informationderived therefrom over said transmitting means and receiving means tothe base station; and calculating means for calculating an amount ofdamage incurred by the component based on said communicated measuredoperational information concerning the respective equipment piece;wherein said operational component is a part in a powertrain of therespective equipment piece.
 4. A communication system between a basestation and a plurality of pieces of construction equipment, saidcommunication system comprising: transmitting means and receiving meansfor transmitting measured operational information from the plurality ofpieces of construction equipment to the base station and wherein eachequipment piece comprises an operational component that is susceptibleto damage; a control means for measuring a plurality of operationalparameters of a respective equipment piece and communicating measuredoperational information derived therefrom over said transmitting meansand receiving means to the base station; and calculating means forcalculating an amount of damage incurred by the component based on saidcommunicated measured operational information concerning the respectiveequipment piece; wherein said operational component is a gear wheel in agear box of the respective equipment piece.
 5. A communication systembetween a base station and a plurality of pieces of constructionequipment, said communication system comprising: transmitting means andreceiving means for transmitting measured operational information fromthe plurality of pieces of construction equipment to the base stationand wherein each equipment piece comprises an operational component thatis susceptible to damage; a control means for measuring a plurality ofoperational parameters of a respective equipment piece and communicatingmeasured operational information derived therefrom over saidtransmitting means and receiving means to the base station; andcalculating means for calculating an amount of damage incurred by thecomponent based on said communicated measured operational informationconcerning the respective equipment piece; wherein said transmittingmeans and receiving means communicate data via radio waves which aretransmitted via satellite.
 6. A communication system between a basestation and a plurality of pieces of construction equipment, saidcommunication system comprising: transmitting means and receiving meansfor transmitting measured operational information from the plurality ofpieces of construction equipment to the base station and wherein eachequipment piece comprises an operational component that is susceptibleto damage; a control means for measuring a plurality of operationalparameters of a respective equipment piece and communicating measuredoperational information derived therefrom over said transmitting meansand receiving means to the base station; and calculating means forcalculating an amount of damage incurred by the component based on saidcommunicated measured operational information concerning the respectiveequipment piece; wherein said control means is further configured formeasuring a first parameter which corresponds to an operational statethat generates damage in the operational component and a secondparameter which corresponds to an operational condition that enhancesdamage imposed on the component by the first parameter.
 7. Acommunication system between a base station and a plurality of pieces ofconstruction equipment, said communication system comprising:transmitting means and receiving means for transmitting measuredoperational information from the plurality of pieces of constructionequipment to the base station and wherein each equipment piece comprisesan operational component that is susceptible to damage; a control meansfor measuring a plurality of operational parameters of a respectiveequipment piece and communicating measured operational informationderived therefrom over said transmitting means and receiving means tothe base station; calculating means for calculating an amount of damageincurred by the component based on said communicated measuredoperational information concerning the respective equipment piece; anddetermination means for determining a total load defined by the totaleffect on the life of the object by the operational state and theoperational condition.
 8. The communication system as recited in claim7, wherein said determination means is further adapted to calculate thetotal load in consideration of variations in damage resistance of theoperational component.
 9. The communication system as recited in claim8, wherein the total load is calculated as a product of a function forthe operational state and a function for the operational condition. 10.A system for wireless communication between a base station and aplurality of vehicles via transmitting and receiving means for checkingthe operational status of the vehicles, wherein each vehicle comprisesan object which is susceptible to damage and means for measuring anumber of operational parameters of the object, wherein the systemcomprises means for calculating damage done to the object based on saidmeasured operational parameters and wherein each vehicle comprisestransmission means for transmitting information regarding the measuredoperational parameters or calculated damage to the base station andwherein the base station comprises microprocessor-based decision meansadapted for automatically controlling future operation of said vehiclesbased on the calculated damage.
 11. The system as recited in claim 10,wherein the vehicles are construction machines.
 12. The system asrecited in claim 11, wherein said object susceptible to damageconstitutes a component in a powertrain.
 13. The system as recited inclaim 12, wherein said object susceptible to damage constitutes a gearwheel in a gear box.
 14. A system for wireless communication between abase station and a plurality of vehicles via transmitting and receivingmeans for checking the operational status of the vehicles, wherein eachvehicle comprises an object which is susceptible to damage and means formeasuring a number of operational parameters of the object, wherein thesystem comprises means for calculating damage done to the object basedon said measured operational parameters and wherein each vehiclecomprises transmission means for transmitting information regarding themeasured operational parameters or calculated damage to the base stationand wherein the base station comprises decision means adapted forcontrolling future operation of said vehicles based on the calculateddamage; wherein the measuring means is adapted for measuring a firstparameter which corresponds to an operational state which generates saiddamage to the object, and at least a second parameter which correspondsto a condition for or around the object that by itself is not able togenerate the damage, but which makes the damage generated by theoperational state worse.
 15. The system as recited in claim 14, whereinthe system comprises means for determining a total load which is definedby the total effect on the life of the object by the operational stateand the operational condition.
 16. The system as recited in claim 15,wherein the determination means is adapted to calculate the total loadin such a way that variations in the damage resistance of the objectwhich the operational condition gives rise to are adjusted for.
 17. Thesystem as recited in claim 16, wherein the total load is expressed as aproduct of a function for the operational state and a function for theoperational condition.
 18. A communication system between a base stationand at least one remotely positioned stationary or mobile machine viatransmitting and receiving means for checking the operational status ofthe machine, with the machine comprising an object which is susceptibleto damage, and wherein the system comprises a control unit, means formeasuring a number of operational parameters of the object, and meansfor calculating damage done to the object based on said measuredoperational parameters; wherein the system comprises a unit arranged totake steps for the future operation of one of the machine and the objectbased on said calculation.
 19. The communication system as recited inclaim 18, wherein said unit for taking steps is a station for spareparts, maintenance or restoration.
 20. The communication system asrecited in claim 18, wherein said unit for taking steps is a facilityfor producing new objects.
 21. A communication system between a basestation and at least one remotely positioned stationary or mobilemachine via transmitting and receiving means for checking theoperational status of the machine, with the machine comprising an objectwhich is susceptible to damage, and wherein the system comprises acontrol unit, means for measuring a number of operational parameters ofthe object, and means for calculating damage done to the object based onsaid measured operational parameters; wherein the system supports afleet of construction machines which are each adapted for communicationwith the base station and wherein the base station comprises decisionmeans adapted for automatically controlling the construction machines.22. The communication system as recited in claim 21, wherein eachconstruction machine comprises transmission means for transmittinginformation regarding at least one of the measured operationalparameters and calculated damage.